# CVE-2026-29972: Memory corruption in n/a

> A stack-based buffer overflow in nanoMODBUS allows remote code execution via malicious Modbus TCP server responses.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 May 2026
- **Updated:** 8 May 2026
- **Also known as:** GHSA-5hc8-p74q-47pp

## What is CVE-2026-29972?

CVE-2026-29972 is a high-severity memory corruption vulnerability in n/a, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

nanoMODBUS through v1.22.0 has a stack-based buffer overflow in recv_read_registers_res() in nanomodbus.c. When a client calls nmbs_read_holding_registers() or nmbs_read_input_registers(), the library writes register data from the server response to the caller-provided buffer based on the response's byte_count field before validating that byte_count matches the requested quantity. A malicious Modbus TCP server can send a response with byte_count=250 (125 registers) regardless of the requested quantity, causing up to 248 bytes of attacker-controlled data to overflow the buffer, potentially allowing remote code execution.

Weakness: CWE-121 (Stack-based Buffer Overflow)

## Which versions are affected by CVE-2026-29972?


## How do I fix CVE-2026-29972?

No fix has been published for CVE-2026-29972 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-29972 being exploited?

There is no known exploitation of CVE-2026-29972 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-29972 and fix it if it is affected.

What it is: CVE-2026-29972 is a high-severity memory corruption vulnerability in n/a, published on 8 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-29972 in the wild and no public exploit code.

Affected product: n/a. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-29972/ (Markdown: https://insights.sbomify.com/CVE-2026-29972/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-29972
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-29972
- OSV: https://osv.dev/vulnerability/CVE-2026-29972

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-29972/
Summaries are generated and may contain mistakes; the official description above is the record.